Lymphocyte Signaling
Our lab focuses on understanding how lymphocytes, especially T cells, get activated at the molecular level. We’re particularly interested in signaling through the T cell receptor (TCR), and over the years, our work has helped shape several key concepts in αβ TCR biology. This includes how the receptor changes its conformation upon antigen binding, how the earliest signaling steps are regulated, and how these events control T-cell activation.
Early TCR Signaling Mechanism
TCR signaling is crucial for adaptive immune responses, yet the exact molecular mechanism linking antigen binding to intracellular phosphorylation has remained elusive. We have demonstrated that TCRs exist in a dynamic equilibrium between an open, phosphorylation-accessible state and a closed, inactive state regulated by cholesterol binding. Antigen binding stabilizes the open conformation, leading to phosphorylation and downstream signaling. Our key findings include:
- TCR ligands (peptides presented by MHC) must induce both clustering and conformational changes for full T-cell activation (Minguet 2007).
- The conformational changes of the TCR regulate ITAM accessibility to the kinase LCK, a key step in TCR signaling (Schamel et al 2017; Swamy 2016).
- A previously unknown RK motif in the CD3ε cytoplasmic tail mediates non-canonical binding of LCK, following ligand-induced TCR structural changes (Hartl et al 2020).
- We’ve also contributed to understanding early TCR signaling through LCK, NCK, and ZAP70 interactions (Schulz et al 2022; Hartl et al 2021; Kästle et al 2020; Wipa et al 2020).
- Dynamic phosphorylation of CD3ε ITAMs is essential for efficient TCR and CAR signaling. Using phospho-mimetic variants, we demonstrated how the CD3ε signalosome contributes to fine-tuning T-cell activation (Woessner et al 2024).
Kidins220 and Caveolin-1 in Lymphocyte Signaling
Beyond TCR signaling, we investigate how adaptor proteins like Kidins220 and Caveolin-1 regulate BCR and TCR pathways:
- Kidins220: We demonstrated that Kidins220 couples resting BCRs to Ras-Raf-Erk signaling (Fiala et al 2015) and promotes multiple B-cell developmental stages. Its absence impacts lambda light chain rearrangement (Schaffer et al 2024). Additionally, Kidins220 modulates TCR signaling strength and invariant natural killer T (iNKT) cell development (Herr et al 2024).
- Caveolin-1: Our studies revealed novel roles of Caveolin-1 in both TCR and BCR signaling, shedding light on its regulatory functions in immune cell activation (Schaffer & Minguet 2020; Fiala & Minguet 2018; Minguet et al 2017; Goetz, Minguet et al 2011).
References
Woessner NM, Brandl SM, Hartmann S, Schamel WW, Hartl FA*, Minguet S*(2024) Phospho-mimetic CD3ε variants prevent TCR and CAR signaling. Front Immunol 15:1392933.
Herr LA, Fiala GJ, Schaffer AM, Hummel JF, Zintchenko M, Raute K, Velasco Cárdenas RMH, Heizmann B, Ebert K, Fehrenbach K, Janowska I, Chan S, Tanriver Y, Minguet S, Schamel WW (2024) Kidins220 and Aiolos promote thymic iNKT cell development by reducing TCR signals. Sci Adv 10(11):eadj2802.
Schaffer AM, Fiala GJ, Hils M, Natali E, Babrak L, Herr LA, Romero-Mulero MC, Cabezas-Wallscheid N, Rizzi M, Miho E, Schamel WWA, Minguet S (2024) Kidins220 regulates the development of B cells bearing the λ light chain. Elife 13:e83943.
Schultz A, Schnurra M, El-Bizri A, Woessner NM, Hartmann S, Hartig R, Minguet S, Schraven B, Simeoni L (2022) A Cysteine Residue within the Kinase Domain of Zap70 Regulates Lck Activity and Proximal TCR Signaling. Cells 11(17):2723.
Hartl FA, Ngoenkam J, Beck-Garcia E, Cerqueira L, Wipa P, Paensuwan P, Suriyaphol P, Mishra P, Schraven B, Günther S, Pongcharoen S, Schamel WWA, Minguet S (2021) Cooperative Interaction of Nck and Lck Orchestrates Optimal TCR Signaling. Cells 10(4):834.
Schaffer A, Minguet S (2020) Caveolin-1, tetraspanin CD81 and flotillins in lymphocyte cell membrane organization, signaling and immunopathology. Biochem Soc Trans 48(6):2387–2397.
Kästle M, Merten C, Hartig R, Kaehne T, Liaunardy-Jopeace A, Woessner NM, Schamel WW, James J, Minguet S, Simeoni L, Schraven B (2020) Tyrosine 192 within the SH2 domain of the Src-protein tyrosine kinase p56Lck regulates T-cell activation independently of Lck/CD45 interactions. Cell Com and Sig 18(183).
Hartl FA, Beck-Garcìa E, Woessner NM, Flachsmann LJ, Velasco Cárdenas RMH, Brandl SM, Taromi S, Fiala GJ, Morath A, Mishra P, Yousefi OS, Zimmermann J, Hoefflin N, Köhn M, Wöhrl BM, Zeiser R, Schweimer K, Günther S, Schamel WW, Minguet S (2020) Noncanonical binding of Lck to CD3ε promotes TCR signaling and CAR function. Nat Immunol 21:902–913.
Wipa P, Paensuwan P, Ngoenkam J, Woessner NM, Minguet S, Schamel WW, Pongcharoen S (2020) Actin polymerization regulates recruitment of Nck to CD3ε upon T-cell receptor triggering. Immunology 159(3):298-308.
Schamel WW, Alarcon B, Minguet S (2019) The TCR is an allosterically regulated macromolecular machinery changing its conformation while working. Immunol Rev 291(1):8-25.
Fiala GJ, Minguet S (2018) Caveolin-1: The unnoticed player in TCR and BCR signaling. Adv Immunol 137:83-133.
Minguet S, Kläsener K, Schaffer AM, Fiala GJ, Osteso-Ibánez T, Raute K, Navarro-Lérida I, Hartl FA, Seidl M, Reth M, Del Pozo MA (2017) Caveolin-1-dependent nanoscale organization of the BCR regulates B cell tolerance. Nat Immunol 18(10):1150-1159.
Schamel WW, Alarcon B, Höfer T, Minguet S (2017) The Allostery Model of TCR Regulation. J Immunol 198(1):47-52. Review.
Swamy, M, Beck-Garcia, K, Beck-Garcia, E, Hartl, FA, Morath, A, Yousefi, OS, Dopfer, EP, Molnar, E, Schulze, AK, Blanco, R, Borroto A, Martín-Blanco N, Alarcon B, Höfer T, Minguet S* and Schamel WWA* (2016) A Cholesterol-Based Allostery Model of T Cell Receptor Phosphorylation. Immunity 44:1091-1101. *Shared corresponding authors.
Fiala GJ, Janowska I, Prutek, F, Hobeika E, Satapathy A, Sprenger A, Plum T, Seidl M, Dengjel J, Reth M, Cesca F, Brummer T, Minguet S* and Schamel WWA* (2015). Kidins220/ARMS binds to the B cell antigen receptor and regulates B cell development and activation. J Exp Med 212(10):1693-708. *Shared corresponding authors.
Goetz JG*, Minguet S*, Navarro I, Samaniego R, Tello M, Calvo E, Lazcano JJ, Osteso T, Pellinen T, Echarri A, Cerezo A, Garcia R, Keely PJ, Sánchez-Mateos P, Cukierman E, Del Pozo MA (2011) Biomechanical remodeling of the microenvironment by stromal caveolin-1 favors tumor invasion and metastais. Cell 146:148-63. *Shared first authorship.
Minguet S*, Huber M, Freudenberg MA, Pollmer C, Reth M, Schamel WW (2008) Enhanced B cell activation mediated by TLR4 and BCR crosstalk. Eur J Immunol 38(9):2475-87 *Corresponding author.
Minguet S, Swamy M, Alarcon B, Luescher IF, Schamel WW (2007) Full activation of the T cell receptor requires both clustering and conformational changes at CD3. Immunity 1: 43-54.
